The present invention relates to a method and apparatus for predetermining or measuring a volume of liquid to be withdrawn from a container. More particularly, the present invention is directed to a method and apparatus in which measuring is performed externally of the container prior to the withdrawing of liquid from the container.
Accurate measuring of liquids from containers is particularly important in agricultural spraying where an aircraft is supplied with a mixture of various chemical materials such as pesticides, etc. When it is desired to withdraw pesticide material from containers or drums and supply the material to a mixing tank, various problems arise.
Pesticides are caustic and can cause damage to individuals who inadvertently breath pesticide fumes. Accordingly, it has been the trend in some states to require that mixing of pesticides be conducted in a "closed mixing system". This refers to the fact that liquid pesticide must be withdrawn from pesticide containers and transported to a mixing tank or the like without the escape of pesticide fumes or liquid into the environment.
It has previously been the practice to insert a conduit such as a suction tube through the top wall of a container for withdrawing liquid pesticide. An adaptor for receiving the suction tube may be provided and prevents the escape of fumes from the container. The liquid pesticide may be withdrawn through the suction tube and transferred to a mixing tank. Such methods satisfactorily enable the withdrawing and transporting of pesticides or other caustic liquids, but it has been difficult to determine the exact amount of liquid volume which has been removed unless expensive measuring devices are used.
For instance, it is known to provide flow meters on conduits which will enable the accurate measurement of a liquid volume being withdrawn from a container. However, flow meters are expensive and may require various modifications to be made to a conduit such as a suction tube. Of course, it may be possible to insert a calibrated depth gauge or rod through the opening in the top wall of the container to determine the amount of liquid therewithin. However, such a practice would defeat the purpose of the requirement of a closed mixing system as well as being generally time consuming and inefficient.
Accordingly, it is a general object of the present invention to provide a method and apparatus which includes a suction tube and a measuring device used in conjunction with one another to determine the amount of liquid volume to be withdrawn from a container. The suction tube is positionable vertically through an opening in the top wall of the container and may be extended until it contacts the container's bottom wall. The suction tube is mounted within a sealed adaptor adjacent the opening so that caustic fumes may not escape. The suction tube is vertically shiftable and a datum is noted on an external portion of the suction tube. The calibrated measuring device is fixed relative to the container and, upon upward shifting of the suction tube, the datum is selectively positioned to correspond with a calibration on the measuring device indicating a preselected liquid volume to be withdrawn.
Another object of the present invention is to provide a method and apparatus, as described above, which will enable the use of a separate measuring device manually positionable adjacent the external portion of the suction tube during a measuring operation.
Still another object of the present invention is to provide a measuring device in which the calibrated scale is inverted, i.e. larger numbers descend to smaller numbers vertically upwardly when the measuring device is in an operative position. The measuring device is calibrated for a specific container having a given, maximum depth relative to its volume.
These and additional objects and advantages of the present invention will be more clearly understood from a consideration of the drawings and the detailed description of the preferred embodiment.